An independent peptide reference — no sellers, every claim sourced

Klotho

Also known as alpha-Klotho, α-Klotho, KL, soluble klotho, sKL

A large longevity-associated membrane protein with strong biology and no consumer product that plausibly delivers it.

preclinical Immune & longevity endogenous peptide

At a glance

Category
Immune & longevity
Status
endogenous peptide
Made from
recombinant Recombinant alpha-klotho protein exists only as a research reagent and in early-stage biotech pipelines; it is a 130 kDa glycoprotein made in cell culture.
Route
intravenous or subcutaneous injection of recombinant protein in animal studies; there is no route by which an oral supplement delivers klotho protein, since a 130 kDa glycoprotein is digested
Half-life
No published human pharmacokinetics for administered klotho. Endogenous soluble klotho is cleared substantially by the kidney, which is one reason levels fall in chronic kidney disease. Any half-life figure attached to a consumer product is unsupported.
Molecular weight
approximately 130 kDa for full-length alpha-klotho; the shed soluble ectodomain is roughly 120-130 kDa
Sequence
Approximately 1012 amino acids (human alpha-klotho), a single-pass type I transmembrane protein with two large extracellular glycosidase-like domains (KL1 and KL2). Far too large to be described as a peptide or synthesised as one.

Alpha-klotho is a human protein encoded by the KL gene, not a drug. There is no approved klotho therapeutic anywhere in the world. Recombinant klotho for injection exists only as a research reagent and in early-stage biotech pipelines; an mRNA-based klotho candidate entered a small phase 1b trial, which is the current state of clinical development. Everything sold to consumers as a 'klotho supplement', 'klotho peptide' or 'klotho activator' is something else: usually an unrelated compound claimed to raise endogenous klotho, or a short fragment with no demonstrated relationship to the protein's function. Klotho is also not a peptide - the full protein is roughly 1012 amino acids and about 130 kDa, and the shed soluble ectodomain is only slightly smaller. No orally available or short-peptide form reproduces it.

Doping status: Not listed by WADA

Checked against the WADA 2026 Prohibited List. For a specific product and country, Global DRO is the lookup athletes are expected to use — the List names substances, not brand names.

No consumer product plausibly contains it: an oral capsule would digest it like any other dietary protein, and no marketed vial has verified content.

This is a short entry. There is little or no published research on this compound, so there is correspondingly little to report. Empty dosing or reconstitution sections mean no credible figures exist — not that they were left out.

Mechanism of action

Alpha-klotho has two distinct functions. As a membrane protein it is the obligate co-receptor that allows FGF23 to signal through FGF receptors, which is how the body regulates phosphate and vitamin D. This function is well established and is why klotho-deficient mice develop hyperphosphataemia, vascular calcification and a syndrome that superficially resembles accelerated ageing - the phenotype in the original 1997 Kuro-o paper is in large part a phosphate-handling disorder, a point often omitted when the mouse is described simply as 'ageing fast'. The ectodomain is also shed into blood, urine and cerebrospinal fluid as soluble klotho, where it acts as a circulating factor independent of FGF23, with reported effects on FGF and Wnt signalling, insulin/IGF-1 signalling, ion channel glycosylation and oxidative stress resistance.

The longevity association is real but is largely correlational in humans. Overexpressing klotho extends lifespan in mice (Kurosu et al., Science 2005) 2. In people, lower circulating soluble klotho is associated with higher all-cause and cardiovascular mortality in several cohorts, particularly in chronic kidney disease and dialysis populations, and certain KL gene variants (the KL-VS haplotype) are associated with cognitive outcomes. Association is not the same as a demonstrated causal lever, and in kidney disease especially the direction is ambiguous: failing kidneys both produce and clear less klotho, so low klotho may be a marker of renal damage rather than a cause of the downstream harm. The most striking interventional result to date is in monkeys rather than humans: Castner and colleagues (Nature Aging, 2023) reported that a single low-dose systemic injection of klotho at 10 mcg/kg improved working memory in aged rhesus macaques, with higher doses of 20 and 30 mcg/kg failing to reproduce the effect 3 - a non-monotonic dose response that is intriguing and unexplained, and that argues against any casual attempt at dosing.

What the research shows

The underlying biology is solid and mainstream - thousands of papers, a clear mechanism in phosphate and FGF23 handling, reproducible mouse lifespan effects on overexpression, and a well-replicated association between low soluble klotho and higher mortality in humans, though the relationship is U-shaped rather than a straight line. What does not exist is a usable therapeutic. No klotho protein product has completed a human efficacy trial, and no consumer product delivers klotho at all.

Research in humans

No completed trial of administered klotho protein with clinical outcomes has been published. The human evidence is observational: cohort studies linking lower serum soluble klotho to higher all-cause and cardiovascular mortality in haemodialysis patients 4 and in chronic kidney disease, and genetic association work on the KL-VS variant. The relationship is not a simple line: the NHANES analysis of middle-aged and older adults found a U-shaped association, with the lowest septile (at or below 575.8 pg/ml) and the highest (at or above 1140.1 pg/ml) both at raised mortality relative to the middle of the range, hazard ratios of roughly 1.46 and 1.38 5. More klotho is therefore not straightforwardly better, which is awkward for any product sold on the premise that it is. Clinical development is at the earliest stage - a phase 1b study of an mRNA-delivered alpha-klotho candidate in healthy adults has begun, with biomarker rather than clinical endpoints. That is the whole of the interventional human record.

Animal and lab research

Kuro-o and colleagues (Nature, 1997) showed that disrupting the mouse klotho gene produces a short-lived phenotype with vascular calcification, osteoporosis, skin atrophy and emphysema 1. Kurosu and colleagues (Science, 2005) showed that klotho overexpression extends mouse lifespan 2. Injected soluble klotho has improved cognition and synaptic function in mice and, at low dose, in aged rhesus macaques 3. AAV-delivered klotho gene therapy has been studied in rodents. The species most relevant to humans - the macaque study - used a single 10 mcg/kg injection with a two-week effect on a memory task 3, which is a narrow finding on a narrow endpoint.

Caveats. The klotho-null mouse is substantially a model of disordered phosphate metabolism, so 'klotho reverses ageing' overstates what the genetics show. Human data are almost entirely observational and heavily confounded by kidney function, which independently drives both klotho levels and mortality. Assays for soluble klotho are not well standardised between studies, so absolute values are not comparable across cohorts 6. The macaque result showed a non-monotonic dose-response that nobody can currently explain, meaning the therapeutic window is unknown. Delivering a 130 kDa glycoprotein systemically, with correct glycosylation and without immunogenicity, is a serious pharmaceutical problem that has not been solved - which is precisely the problem that consumer products silently pretend does not exist.

What it is used for

  • Subject of academic ageing, kidney and neuroscience research
  • Early-stage biotech development target, at phase 1b with an mRNA candidate
  • Marketed to consumers as a 'klotho supplement' or 'klotho peptide' - these products do not deliver klotho protein and there is no evidence they raise it. Note also that more soluble klotho is not straightforwardly better: the NHANES analysis found a U-shaped mortality association, with both the lowest and the highest septiles at raised risk 5

Dosing

  • There is no human dose. The only interventional dosing information in a primate is the single 10 mcg/kg systemic dose in aged rhesus macaques, where higher doses of 20 and 30 mcg/kg did not reproduce the effect 3.
  • That non-monotonic result is a strong argument against extrapolating a dose 3: with a U-shaped or inverted-U response, guessing high is not a conservative error, it simply misses.
  • No consumer product contains recombinant alpha-klotho. An oral capsule cannot deliver a 130 kDa glycoprotein; it would be digested like any other dietary protein. Products claiming to be 'klotho' in vial form are of unverified content and, given the manufacturing difficulty of a correctly glycosylated recombinant protein of this size, are unlikely to be what the label says.
  • Compounds sold as 'klotho activators' are separate substances that should be judged on their own evidence, which is generally thin; a claimed effect on klotho expression in cell culture is not a clinical result.

These figures describe what the literature and published protocols report. They are not advice and not a dosing instruction.

Reconstitution

No reconstitution guidance is given, because there is no legitimate klotho injectable available to a consumer to reconstitute.

Safety

Side effects

  • Unknown for administered klotho in humans; no safety database exists
  • Because alpha-klotho is the co-receptor for FGF23, raising it systemically would be expected to influence phosphate and vitamin D handling - a predictable and potentially clinically significant effect that has not been characterised in people. Klotho-deficient mice develop hyperphosphataemia, vascular calcification, osteoporosis, skin atrophy and emphysema, which is what makes this axis the one to watch 1
  • Immunogenicity against a large recombinant glycoprotein is a substantial theoretical risk, and anti-drug antibodies could in principle neutralise the endogenous protein as well
  • Klotho has been described as a tumour suppressor in some tissues and its signalling interacts with Wnt and IGF-1 pathways; the oncological consequences of chronic elevation are unstudied
  • For consumer products labelled klotho, the relevant risk is simply that the contents are unknown

Do not use if

  • There is no established indication, so in practical terms no one has a demonstrated reason to take it
  • Disorders of phosphate or calcium metabolism, and chronic kidney disease - the population where klotho biology is most disturbed 1 and where an intervention on this axis is least predictable. It is also the population in which the observational mortality associations are strongest and most confounded 45
  • Active or past malignancy - unstudied effects on Wnt and IGF-1 signalling
  • Pregnancy, breastfeeding, children and adolescents - no data

Interactions

Not studied. Mechanistically, any intervention on the klotho axis would be expected to interact with FGF23 biology and therefore with phosphate binders, vitamin D analogues, calcimimetics and the management of chronic kidney disease-mineral bone disorder. None of this has been tested in humans.

Sources